This work is concerned with the modification and development of the air intake system of an existing fuel injection engine of a passenger car in order to meet the following goals: 1. Reduction of the volume occupied by the air duct in bonnet 2. Reduction of the cost of the production 3. Reduction of the weight The new air intake system should be designed such that the engine power, torque and emissions remain unchanged, but resulted in a better performance and lower fuel consumption. By considering the space available around the engine, it is decided to shorten the air duct by movement of filter from back-right of bonnet to front-left, near the throttle. CFD program FLUENT V 5.2 is used to study the duct shortage effects on the air flow enters to the throttle. By taking the same filter and throttle, only the duct between the filter and the throttle is considered for the analysis. A comparison of the experimental data obtained from the constant volume sampling tests and the numerical results shows a good agreement.

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